Understanding how the brain dynamically alters its organization and processing to meet the needs of sensory perception is a crucial question in health and disease. The rat vibrissa (whisker) sensory system is an excellent model in which to explore these issues, as it is a high-resolution sensory system where a great deal is known, in the 'barrel'cortex, about cell type and layer-specific processing. Alpha rhythm is a commonly observed oscillatory brain state that has recently been linked to modulating selective attention. I will test 3 hypotheses related to alpha. First, I will test the prediction (the 'gain modulation'hypothesis), that thalamocortical 7-12 Hz alpha oscillations reduce the amplitude of sensory evoked responses in putative excitatory and inhibitory layer IV neurons. Second, I will test the prediction (the 'sensory modulation'hypothesis) that increased alpha power predicts decreased detection probability for threshold-level stimuli. Third, I will test the prediction (the 'sensory deployment'hypothesis) that in highly trained animals alpha power is modulated as a function of cued attention, effects that will not be observed in no cue periods or when the cue does not predict reward possibility. I will test these hypotheses in head-posted rats trained to detect discrete and well-controlled vibrissa deflections. I will record neural oscillations and excitatory and inhibitory single unit activity using 16-channel laminar recordings during task performance. Ultimately, a more thorough understanding of rhythmic activity in animal models will lead to a better understanding of oscillations in humans. The alpha rhythm explored in this model system is believed to have direct correlates with similar physiological origins in humans. This direction of research has the power of understanding mechanisms behind many disorders, including epilepsy, where such dynamics are altered.